Batteries, once again

[lewisericeric]

Its no secret on the forum that we've had problems with batteries and still don't know why as such!

 

Before Christmas, our batteries ( a 330ah bank) were dropping by around 10 or 11% an hour according to our Smartgauge and we couldn't understand why. We had a guy over who had done a drop test on the batteries and they appeared healthy. Other tests were done on them as well and the batteries are apparently in good nick. Ed Shiers is brilliant if you ever need any engine work doing and a really helpful guy overall. He tested each appliance as well to see how much each item was using.

 

We found out that the inverter alone was using 3.5 amps so decided to get one of these as we only have it on for the TV and aerial anyway most of the time:

 

My link

The pic of the inverter is around half way down.

 

It's a 150w inverter so is fine for use with our TV which is 47w.

 

All was fine until abt a week ago again! We were only going down around 4% an hour and it was brilliant! Now we are back to decreasing to around 10% an hour! What's even more disturbing is that when the batts are at around 70-80% the voltage is showing as around 12.10-12.20!? We have changed all the lights to LED now too.

 

We turn the fridge off around 9PM and every morning before the solar panels kick in, I check for a 'resting voltage' . This morning the resting voltage was 12.75 but the % screen was 74%! I've usually had it where the voltage is lower than the percentage but never the voltage being higher than the percentage!? Is there a problem somewhere with my batts or is my Smartgauge knackered? 12.75 is 90%+ SOC?!

 

Anyone have any ideas what's going on?

 

Just to mention, our Smartgauge did knacker a few months back and was sent back to merlin for repair.

[Chris Pink]

Your 'rest' voltage is probably being dragged up by the solar unless that reading is taken before dawn.

 

If the reading is taken before dawn (and voltage rises damn quick with the least bit of light, especially with MPPT) then it is entirely possible that the

Smartgauge is being confused by your solar.

 

I have been slated again and again for that statement but I stand by it.

[lewisericeric]

Your 'rest' voltage is probably being dragged up by the solar unless that reading is taken before dawn.

 

If the reading is taken before dawn (and voltage rises damn quick with the least bit of light, especially with MPPT) then it is entirely possible that the

Smartgauge is being confused by your solar.

 

I have been slated again and again for that statement but I stand by it.

 

Yes the voltages does Increase rapidly and can even be as high as around 13.6v with even just 3 or 4 Amps from the solar panels but these readings are taken before its light out and the MPPT is in snooze and 0.0 amps coming in.

 

I think what I don't understand is why the voltage it so low with a 47w TV on, and 5 x 1w LED bulbs on - 12.10 voltage ain't right surely?? When I went to bed last night and everything was off.... The voltage after about an hour with all things off had jumped to 12.80 and then the resting voltage this morning after 10 hours of everything being off was 12.70-12.75.

Edited January 20, 2013 by lewisericeric

[Chris Pink]

Then trust the voltage reading and reset the smartgauge. My experience is that it will still appear to go down faster than reality.

 

If that is your voltage in the morning there's nothing wrong with your batteries.

 

The 12.2V is to be expected when you are or have recently been running loads.

 

The voltage under load calculations are complex including such unknowns as the instantaneous internal resistance of the batteries. 12.2V under a 5A load is nothing to worry about, especially as you say it recovers.

[nb Innisfree]

Are you taking voltage readings from the Smartgauge? These readings could be faulty if the Smartgauge is likewise.

[lewisericeric]

Hi chris

 

Thanks for your quick response. I just find it all a bit of a maze - how do I know where I am with my batteries of an evening?! And why has it started going down around 10% when it was only going down 4% on this new inverter. Makes me want to bloody scream!!!

 

Also it could lead to me having my engine on a lot longer than is needed....engine wear and tear, diesel use, annoyance etc!

 

Innisfree - voltage readings are taken from Smartgauge yes but correlate to what shows on my outback MPPt controller which also takes 'live' voltage readings

Edited January 20, 2013 by lewisericeric

[DeanS]

Do it the Dean way.

 

1. Put bag over the Smartguage.

2. Switch on tv.

3. Enjoy the program.

4. Read a book using led lights before bed.

5. Sleep.

6. Wake up.

7. Keep going till invertor beeps. It wont beep in day time, because solar panels will lie to the invertor, telling it voltages are high. At night, voltages will drop, and invertor could beep. To avoid that, run the boat for an hour every afternoon.

8. When this cycle of life fails, buy another battery and add to the bank.

9. Never look at percentages again. You will go mad slowly.

 

Sorted.

[Chris Pink]

7 isn't true, the solar panels will only take the system voltage up if the inverter can't drag it down which it will if the amount of power in the batteries is low.

[bottle]

I have to agree with Chris Pink, just this once,

 

The Smartgauge will be confused by the solar panels but it will correct itself overnight, the voltage readings will be correct on the Smartgauge.

 

I found this out, after recently fitting solar panels.

[ditchcrawler]

I may have missed it, but are you fully recharging your batteries each day?

[Ryeland]

Smartgauge becomes inaccurate after the batteries have reached 50% of their original capacity - see the Smartgauge handbook. My guess is that it becomes more and more pessimistic, probably because the true internal impedance of the batteries is masked by the growing layer of sulphate on the plates (well that's my theory anyway).

 

I am using a knackered set of batteries at the moment, squeezing the last drop of life from them, and I am seeing low voltages, and pessimistic Smartgauge readings, but as long as I can still switch the lights on in the morning, I'm sticking with them!

 

Richard

[wiccan]

Check thst the Smartguage is set to the rightbtype of batteries. I had a similar problem with voltage being different from percentagr and appearing to drop quickly. I then checked the Smartguage battery setting and it was incorrect - read Battery Type 3 AGM/GLASS MAT batteries....I have totally sealed Lead Acid. I chsnged the setting to Option 6. I then ran the engine and used the batteries as normal for around a week or so until the Smartguage caught up......and heypresto the Smartguage snd Voltsge readings now match and I no longet appear to lose vasts amounts.

 

Just a thought - worth looking at

 

As a side note - I did a Factory Reset on the Smartguage which reset the Battery Type to 3 not 1 as it was supposed to.

[lewisericeric]

Thanks for some of the answers.

 

Dean - you've written that as a joke but I so know that's exactly what you'd do!!!

 

The batts are being fully charged to my knowledge. They're no having a 4 hour charge maybe more in the day, and that takes them up to 100% after around 2 1/2 or 3 hours but I leave it on that bit longer - an hour or maybe 2 as I know that 100% reading is never really correct. Then once a week we are giving them an 8hr charge.

 

It's ridiculous. I feel like I'm burning diesel for no reason really as its just not right. Not using any more than 6 or 7 amps at any one time.

 

I've just checked battery type it's set to 1 and we do have wet batts.

 

Rye land - thanks but the voltage is optimistic whereas the percentage is down, and going from past experiences its usually the opposite way round! Also we've had many types of test on the batteries and they were fine.

Edited January 20, 2013 by lewisericeric

[Chris Pink]

You probably are wasting diesel. I think you should cut your daily to 2 to 2.5 hours. You won't notice any difference, it's the 8 hours once a week that counts.

 

Try it for a couple of weeks and see.

 

Bear in mind the weekly cost of batteries as a consumable is almost certainly a lot less than the £10 a week I reckon you're wasting on diesel.

[Bod]

Could the cold weather be having an effect on the batteries?

 

Would it be possible to take voltage reading direct from the battery terminals with a known good independant volt meter?

 

Bod

[nb Innisfree]

I reckon your batts have lost most of their capacity, maybe down to a third or less which would give the Smartgauge headaches, these two things combined could account for your 10% per hour loss.

 

ETA: It's a bit iffy using tests results to ascertain battery condition, it could be a red herring clouding the issue.

Edited January 20, 2013 by nb Innisfree

[lewisericeric]

I reckon your batts have lost most of their capacity, maybe down to a third or less which would give the Smartgauge headaches, these two things combined could account for your 10% per hour loss.

 

ETA: It's a bit iffy using tests results to ascertain battery condition, it could be a red herring clouding the issue.

They've had a drop test done on them though - 583 out of 590 pretty good condition to say they're a year old. We've also had the 690w of solar since may which would maintain the trickle charge that's needed.

 

Also if the were dead capacity wouldn't the resting voltage be showing as maybe 12 or below rather than 12.7-8?

 

They also hold a charge if charged up and then left etc

 

Bod - cheers, I did think that too but surely not to this degree? With the current temperatures is that enough to really affect battery performance?? Isn't it more like if the temperatures are minus 20?!

Edited January 20, 2013 by lewisericeric

[nb Innisfree]

They've had a drop test done on them though - 583 out of 590 pretty good condition to say they're a year old. We've also had the 690w of solar since may which would maintain the trickle charge that's needed.

 

Also if the were dead capacity wouldn't the resting voltage be showing as maybe 12 or below rather than 12.7-8?

 

They also hold a charge if charged up and then left etc

 

Bod - cheers, I did think that too but surely not to this degree? With the current temperatures is that enough to really affect battery performance?? Isn't it more like if the temperatures are minus 20?!

 

Reduced capacity batts will behave like a smaller batt. Our batts have lost quite a bit more than half and still hold their charge well.

[Bod]

I've just found the article that refers to batteries and low tempertures

 

https://www.roadpro.co.uk/images/pdfs/Power%20from%20your%20battery.pdf

 

Its in the Roadpro catalogue for 2011 and on the website for 2013. Scroll down to page 2, half way down on right.

 

Hope they don't mind me putting up the link!

 

Maybe Gibbo can give us the run down on how typical UK tempertures affect batteries.

 

Bod

[smileypete]

At lower temps the charging voltage ideally needs to be a bit higher, as this table in The Battery FAQ shows:

 

http://jgdarden.com/batteryfaq/carfaq9.htm#temp

 

So if the temp is in single figures in °C, the charge voltage could do with being about half a volt higher vs room temp. Not all alts, chargers, solar controllers can do this easily though.

 

Wonder if lewisericeric has an ammeter? That'd be the best way of telling when the batts are fully charged, this bit again in The Battery FAQ give some details:

 

http://jgdarden.com/batteryfaq/carfaq9.htm#charged

 

For a partial daily charge maybe just stop some point before the current has reached that level. I think lewisericeric has enough to be confused by for now

 

cheers, Pete.

~smpt~

Edited January 20, 2013 by smileypete

[lewisericeric]

Thanks guys and that's interesting Bod. I didn't realise just the temperature being at 0 degrees Celsius could reduce a Battery capacity by 25%!

 

someone get gibbo on here, I agree!

[Chris Pink]

Send him a PM, although he is not currently posting he may well respond to a message. He's very helpful.

[lewisericeric]

Will do, cheers again chris

[tosher]

I once had trouble with my bow thruster motor slowing down after a few seconds, the classic signs of a dying battery. I had it drop tested which showed it was fine but I didn't believe it so I bought a new battery. Guess what happened when I fitted the new battery -- just the same. The lesson that a drop test is a pretty good way of testing batteries cost me £80.

[Grace and Favour]

I once had trouble with my bow thruster motor slowing down after a few seconds, the classic signs of a dying battery. I had it drop tested which showed it was fine but I didn't believe it so I bought a new battery. Guess what happened when I fitted the new battery -- just the same. The lesson that a drop test is a pretty good way of testing batteries cost me £80.

 

But if the drop testing "cost you £80" - then look on the bright side - - - you've now got a free battery